dracut-functions.sh: fix inst*() functions for "-H" handling

because some inst*() functions check the existance of the source files
and do not know about the "-H" option, some failed to install the
hostonly files.
ARM: update modules for ARM host only options
base/dracut-lib:pidof() turn off debugging
network: add rd.route parameter
add "--install-optional" and install_optional_items
test/TEST-30-ISCSI: add rd.shell to client root
dracut.sh: add DRACUT_PATH

DRACUT_PATH can now be used to specify the PATH used by dracut
to search for binaries instead of the default
/usr/sbin:/sbin:/usr/bin:/bin

This should be set in the distribution config file
/usr/lib/dracut/dracut.conf.d/01-dist.conf
Merge remote-tracking branch 'upstream/master'